开学时间为2009年2月18日，计算当前日期是第几周

加一label1，用来显示第几周，在加一个button，点击表示计算

代码：

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

namespace WindowsFormsApplication2

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private string s = "2009-2-18";

private int WeekOfYear(string date)

{

DateTime curDay = Convert.ToDateTime(date);

DateTime oldDay = Convert.ToDateTime(s);

int days1 = oldDay.DayOfYear;//获取开学时间离元旦的天数

int days2= curDay.DayOfYear;//获取目前时间离元旦的天数

int days = days2 - days1;

label3.Text = days.ToString();

int daysOutOneWeek = days;

if (daysOutOneWeek <= 0)

{

return 1;

}

else

{

int weeks = daysOutOneWeek / 7;

if (daysOutOneWeek % 7 != 0)

weeks++;

return weeks + 1;

}

}

private void button1_Click(object sender, EventArgs e)

{

string t;

int m;

t = "2009-2-22";

m=WeekOfYear(t);

label1.Text = m.ToString();

}

}

}